Question

当试图在Rust中打印出多维向量的内容时，似乎你不能使用类型Vec<Vec<str>>来表示向量。

fn print_multidimensional_array(multi: &Vec<Vec<str>>) {
    for y in 0..multi.len() {
        for x in 0..multi[y].len() {
            print!("{} ", multi[y][x]);
        }
        println!("");
    }
}

使用此代码，我得到输出：

error[E0277]: the trait bound `str: std::marker::Sized` is not satisfied
 --> src/main.rs:1:1
  |
1 | / fn print_multidimensional_array(multi: &Vec<Vec<str>>) {
2 | |     for y in 0..multi.len() {
3 | |         for x in 0..multi[y].len() {
4 | |             print!("{} ", multi[y][x]);
... |
7 | |     }
8 | | }
  | |_^ `str` does not have a constant size known at compile-time
  |
  = help: the trait `std::marker::Sized` is not implemented for `str`
  = note: required by `std::vec::Vec`

我可以使用哪种类型的矢量来实现这一目标？

Answer 1

使用Vec<Vec<&str>>。

fn print_multidimensional_array(multi: &[Vec<&str>]) {
    for y in multi {
        for v in y {
            print!("{} ", v);
        }
        println!();
    }
}

fn main() {
    let v = vec![vec!["a", "b"], vec!["c", "d"]];
    print_multidimensional_array(&v);
}

另见：

因为我喜欢把事情过于通用......

fn print_multidimensional_array<I>(multi: I)
where
    I: IntoIterator,
    I::Item: IntoIterator,
    <I::Item as IntoIterator>::Item: AsRef<str>,
{
    for y in multi {
        for v in y {
            print!("{} ", v.as_ref());
        }
        println!();
    }
}

fn main() {
    let v1 = vec![vec!["a", "b"], vec!["c", "d"]];
    let v2 = vec![["a", "b"], ["c", "d"]];
    let v3 = [vec!["a", "b"], vec!["c", "d"]];
    let v4 = [["a", "b"], ["c", "d"]];

    print_multidimensional_array(&v1);
    print_multidimensional_array(&v2);
    print_multidimensional_array(&v3);
    print_multidimensional_array(&v4);
}

字符串向量报告错误“str在编译时没有已知的常量大小”

1 个答案: